New tool estimates if solar panels are economic

A new tool is available to help Auckland households and businesses work out whether it makes financial sense to install solar panels on their roofs.

The free online calculator factors in the unique “solar rooftop potential” of half a million Auckland buildings down to one square metre.

This potential depends on such things as the roof’s slope and aspect, and shade from surrounding buildings and trees.

“Solar generation is rapidly rising in New Zealand, with homes leading the trend. We wanted to offer an educational tool that is impartial and realistic to help people work out if solar is economic for their households or workplaces,” says Dr Kiti Suomalainen, a research fellow at the University of Auckland Business School’s Energy Centre.

New Zealand’s total installed solar capacity rose fivefold over the three years to 2017, and Auckland Council has a goal of 970 MW installed capacity of solar photovoltaics by 2040.

3D modelling

She used LiDAR data from Auckland Council, which is collected by planes emitting light pulses and timing how long it took for the reflected pulse to return to the plane, to construct a digital 3D model of the city with all its buildings and trees and other objects. With this, the solar radiation on individual rooftops could be calculated.

The calculator allows users to zoom in on their rooftop for a colour-coded view of its solar energy potential, which highlights the best spots to place panels.

You can also enter the size and quality solar panel you prefer, how much solar power you would use and how much you would sell back to the grid, and several other values.

The calculator gives the total value (savings and revenues minus costs) of the installation over its lifetime. If it is positive, it’s a good investment.